Support for e-resource proxies and url customisers

Some institutions run "proxy servers" (aka "reverse proxies") which are used to proxy requests for eresources in order that a user can access the e-resource with minimal authentication/authorisation issues (e.g. if the proxy server is granted IP authorisation to the resource, the user can access the resource from any location using the proxy server)

There are a variety of proxy servers commonly used by libraries. The most common is probably EZProxy, but there are a number of commercial services as well as homegrown and open source solutions.

This story is to implement support for adding multiple proxy server configurations to a tenant and then including "proxied" URLs in displays and exports.

In order to implement support for proxy servers we will need to:

• Add support for proxy server configurations (including building proxied URLs)
• Add UI for managing proxy server configurations
• Include proxied URLs in exports
• Include proxied URLs in UI where appropriate